Incorporate packing code into repository

[malramsay64]

The packing code https://github.com/malramsay64/2d-packing will allow for finding a range of crystal structures for different shapes of molecules.

This will likely be thorough a CLI outputting a useful format which can then be read into creating a crystal lattice.

Trimer model see: malramsay64/2d-packing#5
Output parameters: malramsay64/2d-packing#6

[malramsay64]

The packing code has now been rewritten in rust and is available at https://github.com/malramsay64/packing

[malramsay64]

This will now involve creating a conda package for the packing code which can then be added as one of the dependencies of this project.